Revert "Revert "ART: Implement X86 hard float (Quick/JNI/Baseline)""

This reverts commit 949c91fb91f40a4a80b2b492913cf8541008975e.

This time, don't clobber EBX before saving it.

Redo some of the macros to make register usage explicit.

Change-Id: I8db8662877cd006816e16a28f42444ab7c36bfef
diff --git a/runtime/arch/x86/context_x86.h b/runtime/arch/x86/context_x86.h
index 8b7804d..c66a9dc 100644
--- a/runtime/arch/x86/context_x86.h
+++ b/runtime/arch/x86/context_x86.h
@@ -61,11 +61,16 @@
 
   void SetGPR(uint32_t reg, uintptr_t value) OVERRIDE;
 
-  bool IsAccessibleFPR(uint32_t reg ATTRIBUTE_UNUSED) OVERRIDE {
-    return false;
+  bool IsAccessibleFPR(uint32_t reg) OVERRIDE {
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfFloatRegisters));
+    return fprs_[reg] != nullptr;
   }
 
-  uintptr_t GetFPR(uint32_t reg) OVERRIDE;
+  uintptr_t GetFPR(uint32_t reg) OVERRIDE {
+    DCHECK_LT(reg, static_cast<uint32_t>(kNumberOfFloatRegisters));
+    DCHECK(IsAccessibleFPR(reg));
+    return *fprs_[reg];
+  }
 
   void SetFPR(uint32_t reg, uintptr_t value) OVERRIDE;
 
@@ -73,9 +78,22 @@
   void DoLongJump() OVERRIDE;
 
  private:
-  // Pointers to register locations, floating point registers are all caller save. Values are
-  // initialized to NULL or the special registers below.
+  // Pretend XMM registers are made of uin32_t pieces, because they are manipulated
+  // in uint32_t chunks.
+  enum {
+    XMM0_0 = 0, XMM0_1,
+    XMM1_0, XMM1_1,
+    XMM2_0, XMM2_1,
+    XMM3_0, XMM3_1,
+    XMM4_0, XMM4_1,
+    XMM5_0, XMM5_1,
+    XMM6_0, XMM6_1,
+    XMM7_0, XMM7_1,
+    kNumberOfFloatRegisters};
+
+  // Pointers to register locations. Values are initialized to NULL or the special registers below.
   uintptr_t* gprs_[kNumberOfCpuRegisters];
+  uint32_t* fprs_[kNumberOfFloatRegisters];
   // Hold values for esp and eip if they are not located within a stack frame. EIP is somewhat
   // special in that it cannot be encoded normally as a register operand to an instruction (except
   // in 64bit addressing modes).